You are planning a take-off in an Echo aeroplane from an aerodrome under the ambient conditions given below.

Ambient conditions for take-off:

Local QNH ........................ 1030 hPa
Wind ................ .... ............140 deg M at 5 kt
Ambient temperature ....... 0 deg C
Aerodrome elevation..........3510 feet
Runway 14/32 surface short dry grass TODA 660 metres
Slope 2% down to the north west

The maximum take-off weight permitted by the Echo take-off performance chart is closest to -

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I worked the PH out to be 3000 using
PH=3510+(1013-1030) x 30
Also for runway options I got:
Runway 14: 2% Up with 5 kt tail wind
Runway 32: 2% Down with 5kt head wind

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However this didn't match the suggested answer:
You can take-off down-hill downwind or up-hill into wind.
Try both. Not much in it really. Down-hill downwind is best.
Pressure Ht 2500ft and zero degrees.
Maximum take-off weight is 2540kg.
The correct answer is: 2540 kg

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Not sure what is the question, however I calculated Density Height DH = 1920,
PH=3000
ISAT=15-(PH/1000x2)=9
ISAD=OAT-ISAT=0-9=-9
DH=PH+(120xISAD)=1920
then you go straight line up from 1920 on the bottom DH axis. Your work is showing DH closer to 1500ft.

I also notice your TODA is closer to 640 than 660 ?
It would be good if you draw both options with slopes and tailwinds.

Again, not sure what is the question as your answer is showing approximately 2540kg ?

My question was that I could not reproduce the suggested solution starting with pressure height. I also got 3000ft, while the suggested solution was "Pressure Ht 2500ft and zero degrees."

For the slope / wind I got:
Also for runway options I got:
Runway 14: 2% Up with 5 kt tail wind
Runway 32: 2% Down with 5kt head wind

while the suggested solution was:
You can take-off down-hill downwind or up-hill into wind.
Try both. Not much in it really. Down-hill downwind is best.

Still stuck with this one. I am not able to come close to the suggested solution.



This is my assessment:
Runway 14: 2% Up with 5 kt tail wind
Runway 32: 2% Down with 5kt head wind

However the solution:
You can take-off down-hill downwind or up-hill into wind.
Try both. Not much in it really. Down-hill downwind is best.

I see my mistake now

Hello, I am new on this and I was observing the explanations and I have a question, can we just use pressure height and the temperature and still be the same as the DH and also what was the mistake you found sir?

I think you really must start paying more attention to what you read, detail and housekeeping. From several of your threads what comes across, very strongly, is carelessness. While this may also be tied up with English as a second language, the reality is that you just MUST overcome the problem. Housekeeping and attention to detail is where it all is.

Runway 14: 2% Up with 5 kt tail wind
Runway 32: 2% Down with 5kt head wind

Are you sure of that ?

You can take-off down-hill downwind or up-hill into wind.
Try both. Not much in it really. Down-hill downwind is best.

Would you like to recheck that, perhaps ?

Pressure Ht 2500ft and zero degrees.

Really ?

Generally, it helps if you copy and paste the whole question that you are working on. That way we don't get confused. I have to say that I don't really know which bits are from the question and which bits are yours ?


can we just use pressure height and the temperature and still be the same as the DH

That should be the case. However, as I have indicated in other threads, these charts are not terribly well drawn. I'll have a look at this one and see how accurate the original work might have been.

I'll have a look at this one and see how accurate the original work might have been.

I've checked a few points. This chart is pretty dreadful with errors spotted up to around 500 ft out on density height.

I've no idea where the chart came from. It doesn't look like anything out of the performance group in the old days and certainly isn't one of mine. Whoever did it was more than a bit rough and ready, I suggest.

That chart is straight out of the CASA workbook for the PEXO exams. ( yes Gavin knows of the errors) doesn't matter apparently.

Sorry, Stuart, I should have been more precise in my comment. My reference was to whoever originally generated the chart rather than its immediate location. Must say I'm surprised by Gavin's response - surely the discrepancies are going to engender dispute along the way. The particular carpet would be a doddle to correct for that consideration ....